The 6.5 will impact your scores. Since it's writing, you can consider revaluation. There is no guarantee it will increase but you will have to spend 1/2 the exam fee on that and there is a 6-8 week wait.
Take some time to improve your skills and try again.
I believe you are still eligible.. because from what I remember, the minimum score needs to be 6.0 bands in each section?
You can include this score in your profile and can update it with your new results as and when you give. The system will reflect updated points based on the new results.